If it is a gun loading trainer, which I believe, this version of Hasegawa in 1/350 scale (Nr. 10 in the manufacturer listing) might be visually of use:

I checked within Super Illustration and found explaining text:
I guess Timmy is spot on regarding recognizing the part then.Super Illustration Yamato - Model Art - Page 88
"... Initially the loading trainer was installed on the deck close to and behind the base of the bridge tower. On the modification a crew stand-by-room was newly built on this position and the gun loading trainer was shifted onto the position next to and to the right of the rear secondary 15.5 cm gun turret. ..."
However, the given book states further
hthSuper Illustration Yamato - ModelArt - Page 88
"... But on her final condition the position was replaced with a triple 25mm machine gun and where the trainer was shifted ultimately is unknown. ...."